Biomedical subjects

K A Tallent

Publications and source records attributed to K A Tallent.

8 recordsLinked to original sources

PubMed2001

Associating semantic space abnormalities with formal thought disorder in schizophrenia: use of triadic comparisons.

Recent studies of schizophrenia have suggested that thought disorder results from abnormalities in semantic processing. In the following pilot study, the cognitive system used for organizing and associating concepts was examined using a triadic comparison task. The semantic maps of schizophrenia patients with high thought disorder (N = 5) were compared to that of schizophrenia patients with low levels of thought disorder (N = 5) and normal controls (N = 10) with multidimensional scaling analysis. At initial testing and at retest, patients with high levels of thought disorder exhibited consistently lower semantic goodness of fit scores and failed to map results of triadic comparisons along well-defined dimensions. Results suggest that thought disorder in schizophrenia is related to a disturbance in the organization of semantic networks.

Adult↗

PubMed2001

Evidence of schizophrenia patients' reduced perceptual biases in response to emotion chimera.

The goal of the study was to determine whether dextral individuals with schizophrenia display atypical perceptual biases in response to faces in general, or whether they display atypical perceptual biases in response to emotional facial cues. To this end, we assessed perceptual processing in schizophrenia patients with four types of free-vision chimeric stimuli. Perceptual biases were evaluated in 45 schizophrenia patients and in 46 controls using two face (emotion, gender) tasks and two nonface (dots, gradients) tasks. In response to the emotion chimera, the patients with schizophrenia displayed a reduced left perceptual bias. The two groups did not differ significantly in their response to the gender chimera or to the two nonface chimera. These findings are consistent with the assertion that schizophrenia patients have impaired emotional perception. In the discussion we consider possible reasons for schizophrenia patients' difficulty comprehending emotional facial stimuli. We suggest that schizophrenia patients' reduced perceptual bias in response to the emotion chimera reflects a hypothesized affective information-processing deficit.

Adult↗

PubMed2001

The association between antisaccade task and working memory task performance in schizophrenia and bipolar disorder.

To date, the research literature has yielded conflicting reports regarding the specificity of antisaccade deficits to schizophrenia. We sought to examine antisaccade and working memory task performance in schizophrenia patients and bipolar patients, as well as to examine the relationship between the two tasks in both patient populations. Thirty-four schizophrenia patients, 20 bipolar patients, and 30 nonpatient controls were administered saccadic inhibition (antisaccade), working memory, and sensorimotor tasks. Compared with the controls, the schizophrenia patients displayed both antisaccade deficits and working memory deficits. In contrast, the bipolar patients produced significantly more errors on the antisaccade task than the controls, though the bipolar group performed similarly to the control group on the working memory task. Mediational analyses demonstrated that working memory partially mediates the relationship between patients' diagnostic group status and antisaccade task performance; working memory performance contributed uniquely to the prediction of antisaccade task performance in the two patient groups. Antisaccade deficits do not appear specific to schizophrenia. The results suggest that in schizophrenia, working memory and antisaccade tasks are tapping similar cognitive processes, whereas in bipolar patients the processes underlying antisaccade and working memory performance are disparate.

Adult↗

PubMed2001

Cognitive slippage in schizotypic individuals.

The Miers and Raulin Cognitive Slippage Scale was used to assess subtle thought disorder, and the Wisconsin Card Sorting Test (WCST) was used to assess cognitive performance in deviantly high scorers on the Perceptual Aberration and Magical Ideation Scales (N = 63), high scorers on the revised Social Anhedonia Scale (N = 62), and in control subjects (N = 83). Results indicate that schizotypic individuals are more likely to report greater cognitive slippage and less likely to achieve as many WCST categories as controls. Individuals with both positive and negative symptoms of schizotypy reported higher levels of cognitive slippage than those individuals reporting only negative schizotypy. Additionally, the results confirm the presence of an especially high-risk group of psychosis-prone individuals, namely, those individuals with deviant scores on the revised Social Anhedonia Scale who possess additional indicators of schizotypy.

Adolescent↗

PubMed1999

Working memory and Wisconsin Card Sorting Test performance in schizotypic individuals: a replication and extension.

The present study examined spatial working memory and Wisconsin Card Sorting Test (WCST) performance in psychosis-prone individuals, either those with extremely high scores on the Social Anhedonia Scale (SocAnh; n = 49) or deviant scores on the Perceptual Aberration-Magical Ideation Scales (Per-Mag; n = 66). Sixty-three individuals with normal scores on the Chapman Psychosis-Proneness Scales served as control subjects. In order to evaluate working memory performance, participants were administered three tasks, namely, sensorimotor, degraded stimulus, and delayed-response tasks. Although the SocAnh and Per-Mag groups displayed poorer performance than control subjects on the working memory task, they did not differ significantly from each other. The SocAnh group exhibited slower reaction times on the working memory task compared to the control group. The groups did not differ in their performance on sensorimotor or degraded stimulus control tasks. Both psychosis-prone groups differed significantly from control subjects in terms of their WCST performance. Working memory performance was inversely associated with the number of perseverative errors (r = -0.17) and the number of trials to complete the first category on the WCST (r= -0.15). These findings extend the literature by indicating that some psychosis-prone individuals with social-interpersonal schizotypal deficits also display subtle spatial working memory impairments.

Adolescent↗

PubMed1999

Wisconsin Card Sorting Test deficits in schizotypic individuals.

The present study investigates executive functioning in schizotypic college students and control subjects using the Wisconsin Card Sorting Test (WCST). Inhibitory control and working memory, two aspects of executive functioning, were examined in deviantly high scorers on the Perceptual Aberration and Magical Ideation Scales (n=97), high scorers on the revised Social Anhedonia Scale (n=58), and in control subjects (n=104). The schizotypic groups displayed significantly more perseverative errors and achieved fewer categories than the control group. The two schizotypic groups did not differ from each other. We identified a subset of schizotypic individuals who also produced clinically deviant WCST profiles. The findings support the hypothesis that executive function deficits may precede the onset of schizophrenia and related illnesses.

Concept Formation↗

PubMed1998

Hemispheric control of motor function: a whole brain echo planar fMRI study.

The aim of this study was to explore whether recruitment of the ipsilateral motor cortex during non-dominant motor movement reflects left hemispheric control of motor function or simply the greater complexity or unfamiliarity of the motor task. BOLD fMRI was performed in normal right-handers during two motor tasks: (1) sequential finger movements (SM task) with the right or left hand; and (2) random finger movements (RM task) with the right hand. In all subjects, activation was predominantly in the contralateral motor areas (primary sensorimotor, lateral premotor, parietal and supplementary motor regions) and ipsilateral cerebellum. While the ipsilateral motor areas were also activated, single subject analysis revealed these areas to be more extensive and to be seen in more subjects during the non-dominant hand SM task and dominant hand RM task than during the more familiar dominant hand SM task. Similarly, group analysis also revealed ipsilateral activation in the primary sensorimotor and lateral premotor areas, but only during the non-dominant SM task and the dominant hand RM task. Non-dominant hand movements, perhaps because they are less 'automatic', appear to require more cortical activity similar to complex tasks with the dominant hand, and result in greater recruitment of ipsilateral cortical motor areas and striatum. The study also illustrates how potentially meaningful subtleties seen on individual maps may be obscured with group averaging approaches.

Adult↗

PubMed1997

Abnormal functional lateralization of the sensorimotor cortex in patients with schizophrenia.

Previous neuroimaging studies have suggested that patients with schizophrenia fail to recruit appropriate focal patterns of cortical responses to cognitive tasks. We investigated whether patients with schizophrenia show a normal focal response to a simple motor task. Seven strongly right-handed patients with schizophrenia and seven strongly right-handed normal subjects performed motor tasks of increasing complexity. Patients were unable to recruit as focal a response even to a simple, automatic sequential finger movement task. They showed greater ipsilateral activation in the primary sensorimotor and lateral premotor regions and had a significantly lower laterality quotient than normal subjects. These phenomena increased with the complexity of the task. These results demonstrate a functional disturbance in the cortical motor circuitry of patients with schizophrenia.

Adult↗